1. Field of the Invention
The present invention relates to a non-pneumatic tire provided with a support structure body supporting a load from a vehicle, serving as a tire structure member, and preferably relates to a non-pneumatic tire which can be used in place of a pneumatic tire.
2. Description of the Related Art
A pneumatic tire has a function of supporting a load, a performance of absorbing a shock from a ground surface, and a performance of transmitting a power (accelerating, stopping and direction changing performance), and is accordingly employed in various vehicles, particularly a bicycle, a motor cycle, an automobile and a truck.
Particularly, these capabilities greatly have contributed to a development of the automobile and other motor vehicles. Further, the shock absorbing performance of the pneumatic tire is useful in a transportation cart for medical equipment and an electronic device, and for other intended uses.
As a conventional non-pneumatic tire, for example, a solid tire, a spring tire, a cushion tire and the like exist, however, they do not have an excellent performance of the pneumatic tire. For example, the solid tire and the cushion tire support the load based on a compression of a ground portion, however, this kind of tire is heavy and rigid, and does not have a shock absorbing performance like the pneumatic tire. Further, in the non-pneumatic tire, it is possible to improve the cushion performance by enhancing elasticity, however, there is a problem that such a load support performance or durability of the pneumatic tire is deteriorated.
Accordingly, in Japanese Unexamined Patent Publication No. 2005-500932, there is proposed a non-pneumatic tire having a reinforced annular band supporting a load applied to a tire, and a plurality of web spokes transmitting a load force by a tensile force between the reinforced annular band and a wheel or a hub, for the purpose of developing a non-pneumatic tire having a similar operating characteristic to the pneumatic tire.
However, in the non-pneumatic tire described in Japanese Unexamined Patent Publication No. 2005-500932, it has been known that a fluctuation of a vertical load tends to be generated due to a positional relationship between a position of the web spoke and a center position of the ground surface, in the case where the vertical load is applied so as to have an identical deflection amount. In other words, in the case where the center position between the web spokes S is positioned at the center TC of the ground surface as shown in FIG. 7A, a reaction force from the tire becomes small (soft), and in the case where a position of a lower end of the web spoke S is positioned at the center TC of the ground surface as shown in FIG. 7B, the reaction force from the tire becomes large (rigid), a circumferential fluctuation of the tire rigidity (which may be, hereinafter, simply referred to as rigidity fluctuation) is seen in a ground state between the both. As a result, there is a risk that uniformity is deteriorated, and various performances are deteriorated due to an uneven grounding.
Further, since the non-pneumatic tire described in Japanese Unexamined Patent Publication No. 2005-500932 has a space between the web spokes which are adjacent in the circumferential direction, the rigidity of the annular band becomes low in a region between the web spokes. Accordingly, the annular band generates a buckling between the web spokes at the time of grounding, and there is a problem that the annular band runs into destruction in addition to a vibration and noise, and an abnormal abrasion of a tread.
In order to suppress such a circumferential fluctuation of the tire rigidity, and in order to prevent the buckling of the ground portion between the web spokes, Japanese Patent No. 3966895 describes a non-pneumatic tire configured by forming a spoke structure body in which fins coupling between an annular outer peripheral member and an inner peripheral member in a diametrical direction are intermittently arranged so as to be spaced in a circumferential direction as a unit structure body which is divided into a plurality of zones in a tire width direction, shifting the positions of the fins in the circumferential direction between the unit structure bodies, forming the unit structure body as a unit structure body which is divided in a plurality of sections in the circumferential direction, and integrating and bonding all the unit structure bodies. The non-pneumatic tire is structured such that the fins which are shifted from each other in the circumferential direction act on an improvement of a rigidity of the outer peripheral member between the fins in the adjacent zones, thereby making the circumferential fluctuation of the tire rigidity small, and suppressing the buckling of the outer peripheral member.
Further, in Japanese Unexamined Patent Publication No. 1-314602, there is described a non-pneumatic tire in which an inner peripheral ring and an outer peripheral ring are coupled by a ring plate shaped web, and a side surface of the web is provided with a rib coupled to the inner peripheral ring and the outer peripheral ring as well as being coupled to the side surface so as to extend sideways.